As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option is an information handling system. An information handling system generally processes, compiles, stores, or communicates information or data for business, personal, or other purposes. Technology and information handling needs and requirements can vary between different applications. Thus information handling systems can also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information can be processed, stored, or communicated. The variations in information handling systems allow information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems can include a variety of hardware and software resources that can be configured to process, store, and communicate information and can include one or more computer systems, graphics interface systems, data storage systems, networking systems, and mobile communication systems. Information handling systems can also implement various virtualized architectures. Data and voice communications among information handling systems may be via networks that are wired, wireless, or some combination.
One subsystem of an information handling system is a storage subsystem. A storage subsystem can be implemented using a redundant array of independent disks (RAID). A RAID storage subsystem comprises a RAID controller and a disk group (DG). The DG comprises a plurality of physical disks (PDs) configured to store information which is presented to the information handling system as being stored on a virtual disk (VD) even though the storage of the information is distributed among the PDs. The VD is thus realized by the DG. A PD of the PDs may be replaced by a replacement PD through the use a member replacement feature of the RAID controller. In existing RAID storage subsystems, a PD cannot be removed to reconstruct a VD using fewer than the existing number of PDs.
In an existing RAID storage subsystem, when the system has multiple disks connected and all the disks are in use (for example, all disks are used for RAID creation), if user is in need of a disk to assign as a hot spare or as hot spares for an important VD or to new create VD, the user has to delete an existing VD to make a PD free and then use it for any other operation.
For example, if the user has created a RAID level 5 VD with four PDs (for example, HDD1, HDD2, HDD3, HDD4) and the user wants to migrate to RAID level 5 with three disks (for example, HDD1, HDD2, HDD3), then the controller would not allow such migration even though RAID level 5 can be utilized with minimum of three PDs. Now, if the user is in need of a disk and doesn't have a free PD for creating new VD or to assign as a dedicated hot spare (DHS) or a global hot spare (GHS), the user cannot perform disk level migration from a RAID level 5 VD realized using four PDs to a RAID level 5 VD realized with three PDs even in a situation where the same VD data capacity can be realized using three of the four PDs.
Currently, if a RAID level 5 VD is created with four PDs (for example, HDD1 (100 GB), HDD2 (100 GB), HDD3 (100 GB), HDD4 (100 GB)) with a VD capacity of 50 GB, the individual used disk space will be 12.5 GB for each PD, where GB stands for gigabytes. Even though HDD1 (12.5 GB/100 GB), HDD2 (12.5 GB/100 GB), HDD3 (12.5 GB/100 GB), and HDD4 (12.5 GB/100 GB) each have little of their available capacity used to store data of the VD, the RAID controller will not allow migration of the VD by removing one of the PDs, for example, such as removing HDD4 (12.5 GB) and splitting its data among the other HDDs (for example, HDD1, HDD2, and HDD3).
The use of the same reference symbols in different drawings indicates similar or identical items.